Refrigeration systems are conventionally known which operate in a refrigeration cycle by circulating refrigerant through a refrigerant circuit, and are widely used for various applications, such as air conditioners. For example, Patent Document 1 discloses a configuration using a so-called hermetically sealed compressor. In the hermetically sealed compressor, a compression mechanism and a motor are contained in a single casing. Furthermore, in the hermetically sealed compressor, an oil feeding channel is formed in the drive shaft of the compression mechanism so that refrigerating machine oil accumulating in the bottom of the casing is fed through the oil feeding channel to the compression mechanism.    Patent Document 1: Published Japanese Patent Application No. 2005-002832